Extendable clasp for a bracelet in particular for a watch

ABSTRACT

The present invention concerns a clasp with an extensible buckle for a bracelet enabling the length of the bracelet to be adjusted. This clasp comprises: a central support ( 1 ); a first and second pivoting strip ( 2   a,    2   b ) articulated at the respective ends of the central support ( 1 ) and capable of being closed on the latter; means for closing and opening ( 14, 16, 17, 19, 22 ) the clasp arranged in such a way as to lock the first and second pivoting strip ( 2   a,    2   b ) against the central support ( 1 ) and to unlock said first and second pivoting strip (2 a,  2 b ) of the central support ( 1 ) so they can be extended; at least one first attachment ( 6   a ) solid with the first pivoting strip ( 2   a ), and arranged to be connected to a first strand of the bracelet and a second attachment ( 6   b ) solid with the second pivoting strip ( 2   b ) and arranged to be able to be linked to a second strand of the bracelet. The clasp according to the invention also comprises an attachment body ( 4 ) arranged on at least one of the first and second pivoting strips ( 2   a,    2   b ), the attachment or each first and second attachment ( 6   a,    6   b ) being connected to the corresponding attachment body ( 4 ), which latter is capable of being displaced in the longitudinal direction of the corresponding pivoting strip ( 2   a,    2   b ) to be locked in various positions along said strip ( 2   a,    2   b ).

The present invention relates to the area of bracelets, particularly for watches. More particularly, it concerns a clasp for a bracelet with an extensible loop enabling precise adjustment of the length of the bracelet.

Clasps with extensible buckles are well known for their aesthetic aspect. These clasps are often associated with bracelets made up of links. The bracelet length is generally adjusted in this case by the retailer by adding or removing one or more links, depending on the size of the wearer's wrist. This adjustment is generally final and does not take into account the differences in wrist circumference dependent on the ambient heat and/or following efforts made by the wearer. However, it has been observed that there often seems to be the need to make such an adjustment, because wrist dimensions change according to whether ambient temperature is high or low. Without the possibility of adjustment, the bracelet may constrict the wrist in hot summer temperatures. Conversely, in winter, that same bracelet tends to turn around the wrist.

There are several watch straps provided with a system that enables watch wearers to adjust the length by just a few millimetres themselves, depending on circumstances. Such clasps are described, in particular, in publications U.S. Pat. No. 5,927,577, JP59108411, EP1716776 EP1378185, EP1943917, EP1920673 or even WO2008064931.

By way of example, the device disclosed in publication U.S. Pat. No. 5,927,577 comprises a bolt, one end of which is articulated at one end of one of the strands of the bracelet, the other end of the bolt being equipped with a rod capable of being positioned inside a case in various holes arranged along the side edges of the latter. The main inconvenience of this device comes from the fact that it is necessary to open the clasp to adjust the length of the bracelet.

JP59108411 relates to a clasp for an extensible buckle with two strips comprising a first and a second strip articulated in relation to each other at one end and an articulated cover at a second end of the first strip, the cover being connected to a first strand of the bracelet. A substantially rectangular opening extends along the longitudinal axis of the second strip. The longitudinal edges of this opening are provided with a notched part arranged to operate in conjunction with fastening means, which are solid with a support of the extensible buckle, the support being connected to a second strand of the bracelet. The fastening means comprise two fastening elements intended to come to be positioned in one of the notches of each notched part of the opening of the second strip in order to lock it in relation to the support of the strip in a desired indexed position. The fastening means furthermore comprises a push button, the action of which enables each fastening element of the corresponding notched part to be disengaged in order to be able to adjust the length of the bracelet. Each fastening element is then positioned in another of the notches of either of the notched parts when the push button is no longer activated in order to lock the second strip in relation to the support strip in another indexed position. Following the example of U.S. Pat. No. 5,927,577, it is necessary to open the clasp to adjust the length of the bracelet, which complicates handling.

EP1716776 discloses a device for adjusting the length of a bracelet which particularly aims to remedy the problem mentioned above. This device comprises a cover, the inside of which is capable of sliding a bolt articulated at one end of the bracelet. This bolt comprises means of pre-positioning and fastening in position, operating in conjunction with a disengaging system enabling the length of the bracelet to be adjusted without having to open said bracelet. According to the information from EP1716776, this adjustment device is intended to be fitted on rigid link bracelets where the ends are provided with a clasp with unfolding articulated strips. Thus, this device is not suitable for leather bracelets or another flexible material, one of the strands of which is intended to be arranged in a passing assembly provided with a tongue for a coarse adjustment of the length of the bracelet.

Publication EP1378185 proposes a clasp with extensible buckle with two strips which solves the problems mentioned above. The two strips of this clasp are articulated around each other at one of their ends while the other of their ends are respectively connected to a cover, connected to one of the strands of a bracelet and to a mobile bolt connected to the other strands of the bracelet. The mobile bolt is arranged inside a receptacle, inside of which are fitted indexation means to adjust the length of the bracelet. These indexation means comprise two fastening elements arranged to operate in conjunction with each other with a part notched in a saw-tooth pattern situated along the lateral internal flanks of the receptacle. Two push buttons provided on the lateral external flanks of the receptacle enable, when they are actuated, the fastening elements of the notched parts to disengage in order to be able to adjust the length of the bracelet.

The aim of the present invention is to propose a different version of an extensible clasp for a bracelet which has the advantage of providing precise adjustment of the length of the bracelet when the clasp is in closed position and which can easily be adapted to be able to be fitted on a bracelet with links or made of leather.

In accordance with the invention, this aim is achieved by a clasp with an extensible buckle for a bracelet enabling the length of the bracelet to be adjusted. This clasp comprises: a central support; a first and second pivoting strip articulated at the respective ends of the central support and capable of being closed on the latter; means for closing and opening the clasp arranged in such a way as to lock the first and second pivoting strip against the central support and to unlock said first and second pivoting strip of the central support; at least one of a first attachment solid with the first pivoting strip, and arranged to be connected to a first strand of the bracelet and a second attachment solid with the second pivoting strip and arranged to be able to be linked to a second strand of the bracelet. The clasp in accordance with the invention furthermore comprises an attachment body arranged on at least one of the first and second pivoting strips. The attachment or each first and second attachment is connected to the corresponding attachment body, which latter is capable of being displaced in the longitudinal direction of the corresponding pivoting strip, to be locked in various positions along said strip.

The characteristics of the invention would be made more clearly apparent by reading the description of a preferential embodiment, given solely by way of example, being in no way limiting and referring to the schematic diagrams, in which:

FIG. 1 shows an exploded view of the clasp with extensible buckle for watch strap according to the preferential embodiment of the invention;

FIG. 2 shows a perspective view from underneath the clasp when the first and second pivoting strips are extended;

FIG. 3 shows a plan view of the clasp when the first and second pivoting strips are closed on the central support;

FIG. 4 shows a cross-sectional view of FIG. 3 along the section A-A in which the first and second attachment are each in a first indexed position;

FIG. 5 shows a side view of the side of the clasp in which the first and second attachment are each in a second indexed position;

FIG. 6 shows a cross-sectional view of FIG. 3 along section H-H;

FIG. 7 shows a cross-sectional view of FIG. 4 along section B-B;

FIG. 8 shows an exploded view of one of the pivoting strips comprising the attachment body;

FIG. 9 shows a plan view of the assembled pivoting strip of FIG. 8 when the attachment body is in a first indexed position;

FIG. 10 shows a cross-sectional view of FIG. 9 along section C-C;

FIG. 11 shows a plan view of the of the pivoting strip when the attachment body is in a second indexed position;

FIG. 12 shows a cross-sectional view of FIG. 11 along section D-D.

The clasp in accordance with the invention enables a useful adjustment of the length of a bracelet. Seen particularly from FIGS. 1 to 3, this clasp is of a three-strip extensible buckle type and thus comprises a first and a second pivoting strip 2 a, 2 b articulated at the respective ends of a central support 1 around an axis 3 so they can be closed and locked against this support 1. This is of elongated shape following the longitudinal direction of the bracelet and slightly curved inwards better to merge with the shape of a wearer's wrist.

Each pivoting strip 2 a, 2 b has a hollow 5 of rectangular shape in which an attachment body 4 is provided. This comprises at one end a buckle 6 a, 6 b intended to receive a bar, respectively of a first and second strand forming the bracelet (not illustrated). Each attachment body 4 is arranged to be actuated in translation inside the hollow 5 along the longitudinal edges 2, 2′ of each pivoting strip 2 a, 2 b in order to be able to be locked in various positions indexed in relation to the corresponding pivoting strip by means of a locking device. When the clasp in accordance with the invention is fitted onto a bracelet and the two attachment bodies 4 are displaced along their respective hollow in the longitudinal direction of the corresponding strip to be locked in a position close to the centre of support 1 (FIG. 4), the length of the bracelet is shortened while this length is extended when the attachment bodies 4 are displaced in the direction of the side edges of the central support 1 (FIG. 5).

The locking device of each attachment body 4 has a bolt 7 connected to each pivoting strip 2 a, 2 b and arranged to operate in conjunction with the corresponding attachment body 4. The bolt 7 is capable of occupying a first and a second axial position respectively. When the bolt 7 is situated in one of its two axial positions, the attachment body 4 is locked in one of the various indexed positions while this body 4 is unlocked in translation when the bolt 7 is situated in the other of the two axial positions. In this latter configuration, the attachment body 4 may slide inside the hollow 5 along the longitudinal edges 2, 2′ of the corresponding pivoting strip 2 a, 2 b to assume another indexed position.

More particularly, especially with reference to FIG. 7 and FIG. 8, the bolt 7 is arranged to cross the longitudinal edges 2, 2′ of each pivoting strip 2 a, 2 b as well as the attachment body 4 along an axis perpendicular to the displacement of said body 4. Thus, the latter comprises an elongated opening 8 (FIG. 10) the thickness of which is slightly greater than the diameter of the central part of the bolt 7, in order to enable the displacement of the body 4 inside the hollow 5 of the pivoting strip. The lower and upper part of the opening 8 each preferably comprises three recesses 9 a, 9 b and 9 c as illustrated by FIG. 8 and FIG. 12 in particular. These recesses are intended to accommodate a bulge 7 a situated on one of the sides of the central part of the bolt 7 when this is located in one of its two axial positions (FIG. 7), thus locking the attachment body 4 in relation to the pivoting strip. The bulge 7 a is disengaged from the body 4 when the bolt 7 is located in the other of its two axial positions in order that said body 4 can be displaced in relation to the pivoting strip in another indexed position. The two ends of bolt 7 accommodate the push buttons, pressing on either of the ends of which enable the bolt 7 to be guided into either of its two axial positions.

A pawl 10 is arranged in each of the two longitudinal edges 2, 2′ of each pivoting strip 2 a, 2 b preferably to operate in conjunction with three recesses 11 situated on the corresponding attachment body 4. These pawls 10 have the function of pre-positioning each body 4 in one of the various indexed positions before displacing the corresponding bolt 7 from either of its two axial positions in order to lock the attachment body to the corresponding pivoting strip.

Referring again to FIG. 1 to FIG. 3 the central support 1 of the clasp comprises two side structures 12, 12′ the internal flanks of which comprise notches 13 intended to accommodate either end of the bolt 7 of each pivoting strip 2 a, 2 b when they are engaged to be closed against said support 1. The means for locking/unlocking pivoting strips 2 a, 2 b comprise two push buttons 14 arranged on either end of the central support 1 partially inside a bed 15. Two compression springs 16 are provided in each bed 15 against the corresponding push button 14 and from either end of the two rods 17 connected to the push button. The two rods 17 of each push button 14 are extended inside the two holes 18 made in each side structure 12, 12′ of the central support 1 to be able to be connected to a stud 19 by means of a pin 20. The two studs 19 are arranged above a rectangular plate 21 which connects the two side structures 12, 12′ and operate in conjunction with retaining means 22 arranged at one end of the first and second pivoting strips 2 a, 2 b in order to lock the latter against the central support 1. These studs 19 are arranged to displace along the plate 21 against each other in a direction perpendicular to the longitudinal axis of the pivoting strips when the two push buttons 14 are actuated simultaneously in order that the said studs 19 are disengaged from the retention means 22 of the pivoting strips 2 a, 2 b so that they can be extended.

More precisely, each stud 19 has a triangular prism 23 on two opposite faces, oriented in such a way that one of these faces is arranged in a plane of 45° relative to the base of the stud. The prisms 23 of each stud 19 come into contact with chamfers 24 (FIG. 8) situated on the pivoting strips 2 a, 2 b when they are closed on the central support 1. A pressure exerted on the end of each strip enables the studs 19 to be displaced until each prism 23 is situated opposite a notch 22, into which it is introduced under the action of compression springs 16 of each push button 14 thus locking the strips against the support 1. The respective prisms 23 are disengaged from the corresponding notches 22 when the two push buttons 14 are activated simultaneously in order to enable the extension of the pivoting strips 2 a, 2 b.

Of course, the invention is not limited to the embodiment described above by way of example but it comprises all other variations of operation covered by the claims. By way of example, the means to enable extension or shortening of the bracelet may be arranged solely on one of the pivoting strips, the other pivoting strip being configured to be connected to a strand of the bracelet by any type of attachment system. 

1. Clasp with an extensible buckle for a bracelet enabling the length of the bracelet to be adjusted, said clasp comprising: a central support (1), a first and second pivoting strip (2 a, 2 b) articulated at either end of the central support (1) and capable of being closed on the latter, means for opening and closing (14, 16, 17, 19, 22) the clasp arranged in such a way as to lock the first and second pivoting strip (2 a, 2 b) against the central support (1) and to unlock said first and second pivoting strip (2 a, 2 b) from the central support (1) so they can be extended, at least one of a first attachment (6 a) solid with the first pivoting strip (2 a) and arranged so as to be connected to a first strand of the bracelet and a second attachment (6 b) solid with the second pivoting strip (2 b), and arranged so as to be connected to a second strand of the bracelet; characterised in that the clasp furthermore comprises an attachment body (4) arranged on at least one of the first and second pivoting strips (2 a, 2 b), the attachment or each first and second attachment (6 a, 6 b) being connected to the corresponding attachment body (4), which latter is capable of being displaced in the longitudinal direction of the corresponding pivoting strip (2 a, 2 b) to be locked in various positions along said strip (2 a, 2 b).
 2. Clasp according to claim 1, characterised in that at least one of the pivoting strips (2 a, 2 b) is provided with an elongated hollow (5), the corresponding attachment body (4) being capable of sliding inside the hollow (5) along the longitudinal edges (2, 2′) of the corresponding pivoting strip (2 a, 2 b), then being locked in translation in one of the various indexed positions in relation to said strip (2 a, 2 b).
 3. Clasp according to claim 1, characterised in that the pivoting strip or each pivoting strip (2 a, 2 b) comprises a bolt (7) arranged to operate in conjunction with the corresponding attachment body (4), the bolt (7) being capable of assuming respectively a first and a second axial position so that the attachment body or each attachment body (4) can be locked in one of the various indexed positions when the bolt (7) is situated in one of the first and second axial positions, and in such a way that the attachment or each attachment body (4) can be unlocked in order to be able to slide inside the corresponding hollow (5) to assume another indexed position when the bolt (7) is situated in the other of the first and second axial positions.
 4. Clasp according to claim 3, characterised in that the bolt (7) is arranged to cross the longitudinal edges (2, 2′) of the pivoting strip or each pivoting strip (2 a, 2 b) as well as the attachment body (4) along a perpendicular axis in the direction of displacement of the said body (4).
 5. Clasp according to claim 3, characterised in that the attachment body or each attachment body (4) comprises an opening (8), the lower and/or upper edge of the opening (8) comprising several recesses (9 a, 9 b, 9 c) spaced in the direction of displacement of the attachment body (4) and in that the bolt (7) comprises a bulge (7 a) arranged to come to be accommodated in one of the recesses (9 a, 9 b, 9 c) in order to lock the attachment body or each attachment body (4) in one of the various indexed positions while the bolt (7) is situated in one of the first and second axial positions.
 6. Clasp according to claim 1, characterised in that a pawl (10) is arranged in at least one of the longitudinal edges (2, 2′) of the pivoting strip or each pivoting strip (2 a, 2 b) to operate in conjunction with several recesses (11) situated on the corresponding attachment body (4) in order to pre-position said body (4) in one of the various indexed positions before displacing the corresponding bolt (7) from any one of its two axial positions in order to lock said body (4).
 7. Clasp according to claim 3 characterised in that the central support (1) of the clasp comprises two side structures (12, 12′), the internal flanks of which comprise notches (13) for accommodating any one end of the corresponding bolt (7) when the first and second pivoting strips (2 a, 2 b) are closed on said support.
 8. Bracelet comprising the clasp according to claim
 1. 9. Watch comprising the bracelet according to claim
 8. 